This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the disclosed methodologies and techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
To produce hydrocarbons from subsurface accumulations or formations, a development plan is typically utilized. The development plan may include a reservoir depletion scheme and a reservoir surveillance strategy. Such reservoir surveillance strategy may include monitoring the production fluids for detection and prediction of static reservoir compartmentalization and to determine the mixing proportions of different reservoir intervals in a co-mingled hydrocarbon phase for the long term delivery of hydrocarbons (e.g., production allocation). An additional consideration in reservoir development is predicting how reservoir performance may change over production timescales of up to 10 s of years. The prediction of dynamic changes in hydrocarbon producibility from individual compartments, intervals and individual reservoirs typically relies on measurements of in-situ fluid properties, such as from P-V-T studies, and may be influenced by chemical or physical processes, such as liquid drop out, for example.
An effective technique to mitigate the effects of chemical or physical processes that may negatively impact reservoir performance is through the monitoring of geochemical and physical parameters (such as pressure). That is, a change in conditions may be identified and then adjustments to the production of hydrocarbons are performed. Indeed, petroleum geochemistry has been applied to several aspects of reservoir surveillance based on the variability of fluid compositions within the same compartments, intervals or reservoirs. See e.g., Larter and Aplin, (1995). See, e.g., Larter, S. R., and Aplin, A. C. Reservoir geochemistry: methods, applications and opportunities. Geological Society of London Special Publication, 86, 5-32, 1995. For example, isotopic and molecular compositional analyses of hydrocarbons and/or water provide different signatures of reservoir hydrocarbon products and waters when differences in signatures exist between intervals or compartments. However, these isotopic and compositional signatures have limited application in static reservoir surveillance applications when the geochemical signatures of hydrocarbons derived from different reservoirs or compartments in the area of interest are indistinguishable. Additionally, in dynamic reservoir surveillance applications, traditional techniques are reactive to the onset of such processes and do not provide advance indications of impending changes in reservoir fluid properties. This is exacerbated by the fact that there is a paucity of tracers available to conduct reservoir surveillance in predominantly natural gas reservoir systems. Indeed, at present typically only bulk organic and inorganic geochemistry and/or stable isotope systematics of carbon and hydrogen are utilized in such investigations or monitoring practices. Furthermore, bulk composition and stable isotopes can provide information on source, maturation and the extent of alteration processes such as biodegradation. These techniques do not provide insights into physical processes, such as phase transformations, liquid drop-out or degassing of formation water, nor do they allow for estimates of HC volume changes that occur during production from a compartment, interval or reservoir (region of interest).
As a result, enhancements to geochemical tracers are needed for reservoir surveillance. These indictors may provide a greater variability than current tracers and display sensitivity to chemical and/or physical processes to provide a more effective static and dynamic reservoir surveillance monitoring techniques. In this manner, the depletion strategies may be adjusted to improve hydrocarbon production and advance our understanding of long-term assessment and management practices.